Processing apparatus for electroplating conductive bumps on organic circuit board

ABSTRACT

A processing apparatus for electroplating conductive bumps on an organic circuit board includes a surface cleaning unit for removing organic contaminant on the surface of conductive layer on the circuit board, a rinsing unit for rinsing the surface of conductive layer, a surface activating unit for removing a metal oxide on the surface of conductive layer, and an electroplating unit for electroplating a conductive bump on the exposing surface of the conductive layer. Thus, the conductive bumps are formed on the circuit board by electroplating. As a result, the alignment is easier, the bonding strength is reinforced, and the requirement for high density fine-pitch bumps is met

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 USC 119 of Taiwan ApplicationNo. 094114847, filed on May 9, 2005.

FIELD OF THE INVENTION

The present invention relates to a processing apparatus for formingconductive bumps on a circuit board, and more particularly, to aprocessing apparatus for electroplating conductive bumps on an organiccircuit board.

BACKGROUND OF THE INVENTION

Compared to wire bonding technique, the flip-chip packaging techniqueintroduced by IBM Corp in early 1960 is characterized by the employmentof conductive bumps for electrically connecting the semiconductor chipand the substrate instead of the traditionally used gold wires. Theadvantages of the flip-chip packaging technique include increasedpackage density and reduced package size. Meanwhile, the flip-chippackaging technique eliminates the need for long-length metal wires,thus reducing the resistance and increasing electrical conductivity.

In current flip-chip technique, electrode pads are disposed on theelectrical surface of the semiconductor Integrated Chip (IC) chip,whereas electrical conductive pads are formed on organic circuit board,so as to conductive bumps or other conductive adhesives can beappropriately placed between the semiconductor chip and the circuitboard. As a result, the chip can be disposed on the circuit board in aface-down manner, wherein the conductive bumps or conductive adhesivesprovide electrical I/O and mechanical connection between the chip andcircuit board.

FIG. 1 illustrates a conventional flip-chip package. As shown, aplurality of conductive bumps 11 are formed on electrode pads 12 of achip 13 and pre-solders 14 made of solders are formed on the electricalconductive pads 15 of an organic circuit board 16. Under a reflowtemperature that is sufficient to fuse the pre-solders 14, thepre-solders 14 are reflowed to the corresponding conductive bumps 11,forming solder contacts 17.

Referring now to FIGS. 2A to 2C, an organic circuit board 2 used forconventional flip-chip package is shown. The circuit board 2 is formedwith a plurality of electrical conductive pads 21, typically made ofmetal materials (e.g. copper). Thereafter, an organic insulatingprotective layer 22 is formed on the circuit board, such as a soldermask to protect the circuit layer on the circuit board and provideinsulation. A plurality of openings 22 a is formed on the insulatingprotective layer 22 to expose the electrical conductive pads 21 on thecircuit board 2. Then, soldering materials are deposited on theelectrical conductive pads 21 of the circuit board 2 by stencil printingtechnology and reflowed to form conductive bumps. As shown in FIG. 2A, astencil 23 with meshes 23 a is first provided on the circuit board 2,then soldering material 24 is placed on the stencil 23 and a roller isrolled back and forth on the stencil 23 to squeeze the solderingmaterial 24 into the meshes 23 a of the stencil 23; or alternatively,the soldering material 24 is sprayed into the meshes 23 a of the stencil23. As shown in FIG. 2B, after the stencil is removed, soldering dotsare formed on the electrical conductive pads 21 of the circuit board 2.Thereafter, as shown in FIG. 2C, reflow of the solder is performed undera temperature sufficient to melt the soldering dots and form conductivebumps 24 a on the electrical conductive pads for subsequent formation ofsolder contacts.

Along with the rapid improvement in various portable products in areassuch as communication, network and computer, BGA (Ball Grid Array), flipchip, CSP (Chip Size Package) and MCM (Multi-Chip Module) packageshaving the characteristics of reduced IC area, high density and high pincounts have become the mainstream of the packaging market. Thesepackages demand a smaller line width and pad size. However, if the padpitch keeps reducing, the electrical conductive pads will be partiallyblocked by the insulating protective layer. As a result, the pad sizeexposed from the insulating protective layer is even smaller, whichbecomes an issue in subsequent alignment of conductive bumps.Furthermore, due to the space occupied by the insulating protectivelayer and its height, the stencil aperture in the stencil printingtechnology has to be reduced, which creates problems for stencil makingand increases its cost. Additionally, the aperture may even be too smallfor the soldering material to pass through.

Moreover, the forming of soldering materials requires not only the sizeof the stencil to be accurate, but also the number of printing andcleaning to be taken into account. Since soldering material has acertain viscosity, when the number of printing gets larger, the residualsoldering material left in the wall of the stencil holes is greater,which may result in the amount and shape of soldering material in thenext printing not meeting the design specification. Thus, in actualoperations, stencil must be cleaned after a certain number of usages.

Therefore, there is a need for a method for efficiently formingpre-solders on an IC package substrate that provides finer pitch andavoids poor alignment of soldering materials, weak bonding and low yieldin stencil printing technique.

SUMMARY OF THE INVENTION

In the light of forgoing drawbacks, an objective of the presentinvention is to provide a processing apparatus for electroplatingconductive bumps on an organic circuit board, such that high densityconductive bumps can be electroplated on the circuit board.

Another objective of the present invention is to provide a processingapparatus for electroplating conductive bumps on an organic circuitboard that reduces difficulty in bump alignment.

Still another objective of the present invention is to provide aprocessing apparatus for electroplating conductive bumps on an organiccircuit board that improves poor bonding of the conductive bumps on theelectrical conductive pads of the circuit board.

Yet another objective of the present invention is to provide aprocessing apparatus for electroplating conductive bumps on an organiccircuit board that allows quick and precise forming of the conductivebumps, improving reliability of the manufacturing process.

In accordance with the above and other objectives, the present inventionprovides a processing apparatus for electroplating conductive bumps onan organic circuit board, comprising: a surface cleaning unit forremoving organic contaminant from an exposed surface of a conductivelayer of the circuit board; a rinsing unit for rinsing the surface ofthe conductive layer; a surface activating unit for removing a metaloxide formed on the surface of the conductive layer; and anelectroplating unit for electroplating conductive bumps on the surfaceof the conductive layer. The circuit board further comprises a pluralityof electrical conductive pads. An insulating protective layer withpatterned openings for exposing the electrical conductive pads iscovered on the surface of the circuit board, and a photoresist havingopenings corresponding to the electrical conductive pads of the circuitboard is formed on the conductive layer to partially expose theconductive layer overlying the electrical conductive pads. The organiccontaminant and metal oxide are respectively removed from the surface ofthe conductive layer by the surface cleaning unit and the surfaceactivating unit and the surface of the conductive layer is cleaned againbefore conductive bumps are electroplated thereon.

The processing apparatus may further comprise a post-treatment unithaving a rinsing unit and a cleaning unit to rinse the circuit boardwith the conductive bumps thereon and remove the photoresist.

Another embodiment of the processing apparatus of the present inventioncomprises: a surface cleaning unit for removing organic contaminant froman exposed surface of a conductive layer of the circuit board; a firstrinsing unit for rinsing the surface of the conductive layer; a firstsurface activating unit for removing a metal oxide formed on the surfaceof the conductive layer; a first electroplating unit for forming a basemetal on the surface of the conductive layer; a second rinsing unit forrinsing the surface of the base metal; and a second electroplating unitfor electroplating conductive bumps on the surface of the base metal.

The processing apparatus may optionally comprise a second surfaceactivating unit for removing a metal oxide formed on the surface of thebase metal, so as to facilitate subsequent formation of the conductivebumps on the surface of the base metal.

As a result, poor alignment, weak bonding and low yield in conventionalstencil printing technique can thus be avoided and finer bump pitch canbe achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thefollowing detailed description of the preferred embodiments, withreference made to the accompanying drawings, wherein:

FIG. 1 (PRIOR ART) is a cross-sectional diagram of a conventionalflip-chip package;

FIGS. 2A to 2C (PRIOR ART) are cross-sectional diagrams illustratingforming conductive bumps on a circuit board by stencil coating;

FIG. 3 is a block diagram illustrating an embodiment of the processingapparatus for electroplating conductive bumps on organic circuit boardof the present invention;

FIGS. 4A to 4D″ are cross-sectional diagrams illustrating formingconductive bumps on a circuit board of the present invention; and

FIG. 5 is a block diagram illustrating another embodiment of theprocessing apparatus for electroplating conductive bumps on organiccircuit board of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention relates generally to a processing apparatus forforming conductive bumps on a circuit board, and more particularly, to aprocessing apparatus for electroplating conductive bumps on an organiccircuit board. The following description is presented to enable one ofordinary skill in the art to make and use the invention and is providedin the context of a patent application and its requirements. Variousmodifications to the preferred embodiments and the generic principlesand features described herein will be readily apparent to those skilledin the art. Thus, the present invention is not intended to be limited tothe embodiments shown, but is to be accorded the widest scope consistentwith the principles and features described herein.

First Embodiment

FIG. 3 shows the processing apparatus for electroplating conductivebumps on organic circuit board of the present invention. The processingapparatus mainly forms conductive bumps on circuit board. Referring toFIGS. 4A to 4D in conjunction, as shown in FIG. 4A, a circuit board 40with electrical conductive pads 42 formed thereon is first provided,which can be a two-layer or multi-layer circuit board that has completedcircuit layout. An insulating protective layer 41 with patternedopenings 41 a is formed on the surface of the circuit board, wherein theelectrical conductive pads 42 are exposed through the patterned openings41. The electrical conductive pads can be connected to inner circuitsvia conductive vias (not shown). A conductive layer 42 is formed on theinsulating protective layer 41 covering the electrical conductive pads42. A photoresist 44 is further formed on the conductive layer 42.Openings 44 a corresponding to the electrical conductive pads 42 of thecircuit board 41 are formed on the photoresist 44 to expose theconductive layer 43 on the surface of the electrical conductive pads 42.

The processing apparatus for forming conductive bumps comprises: asurface cleaning unit 31, a rinsing unit 32; a surface activating unit33 and an electroplating unit 34. The surface cleaning unit 31 is usedfor removing organic contaminant 45 on the surface of the conductivelayer 43 of the circuit board 40, FIG. 4A shows the structure before theorganic contaminant 45 are removed and FIG. 4B shows the structure afterthe organic contaminant are removed from the circuit board 40. Thesurface cleaning unit 31 is a cleanser with surfactant to remove theorganic contaminant 45 on the surface of the conductive layer 43. Therinsing unit 32 is used to rinse the surface of the conductive layer 43.The surface activating unit 33 is used to remove a metal oxide 46 formedon the surface of the conductive layer 43, as shown in FIG. 4C. Theelectroplating unit 34 is used to perform electroplating on the exposedsurface of the conductive layer 43 to form conductive bumps 47. Theconductive bumps can be copper, tin, lead, nickel, gold, silver, bismuthor their alloy, as shown in FIG. 4D.

The processing apparatus 30 may further comprise a post-treatment unit35 having a rinsing unit and cleaning unit, so as to make a finalcleaning of the circuit board 40 formed with the conductive bumps 47, aswell as to remove the photoresist on the surface of the circuit board.

Since the conductive bumps 47 are electroplated on the electricalconductive pads 42 through the conductive layer 43, so before theconductive bumps 47 are formed, the surface activating unit 33 must beused to remove the metal oxide 46 on the surface of the conductive layer43, such that the conductive layer 43 has a clean surface for subsequentforming of the conductive bumps 47. In addition, the surface activatingunit 33 further comprises the effect of prewetting the circuit board 40,so as to increase the wetting of the surface of the conductive layer 43of the circuit board to facilitate formation of the conductive bumps 47thereon.

Second Embodiment

FIG. 5 shows another embodiment of the processing apparatus of thepresent invention. The difference of this embodiment with the previousone is in that a base metal is first electroplated on the top of theelectrical conductive pads 42 of the circuit board 40, and conductivebumps are then formed on the base metal.

The processing apparatus 50 in this embodiment comprises: a surfacecleaning unit 51, a first rinsing unit 52; a first surface activatingunit 53; a first electroplating unit 54; a second rinsing unit 55; asecond surface activating unit 56 and a second electroplating unit 57.The surface cleaning unit 51 is a cleanser with surfactant to remove theorganic contaminant 45 on the surface of the exposed conductive layer43. The first rinsing unit 52 is used to rinse the surface of theconductive layer 43 to remove residuals from the last process. The firstsurface activating unit 53 is used to remove a metal oxide 46 formed onthe surface of the conductive layer 43. The first electroplating unit 54is used to form a base metal 48 on the surface of the conductive layer43, as shown in FIG. 4D′. The second rinsing unit 55 is used to rinsethe surface of the base metal 48 to remove residuals from the lastprocess. The second surface activating unit 56 is used to remove a metaloxide 46 formed on the surface of the base metal 48. The second surfaceactivating unit 56 can be selectively used. If the base metal 48 ischemically active, i.e. oxide may easily formed thereon, then the secondsurface activating unit 56 can be used; else if the base metal 48 ischemically inactive, i.e. oxide may not easily formed thereon, then thesecond surface activating unit 56 can be omitted. The secondelectroplating unit 57 is used to form conductive bumps 49 on thesurface of the base metal 48, as shown in FIG. 4D″.

The processing apparatus 50 may further comprise a post-treatment unit58 having a rinsing unit and cleaning unit, so as to make a finalcleaning of the circuit board 40, as well as to remove the photoresist44 on the surface of the circuit board 40.

The processing apparatus 50 first forms the base metal 48 on theelectrical conductive pads 42 of the circuit board 40 through theconductive layer 43 by electroplating, then forms the conductive bumps49 by electroplating. Before the first electroplating unit is used,metal oxide is first removed using the first surface activating unit 53.After the base metal 48 is formed, the second surface activating unit 56for removing metal oxide on the surface of the base metal 48 can beselectively used. Thereafter, the second electroplating unit 57 is usedto form the conductive bumps 49 on the base metal 48.

The present invention employs exposure-development method for formingopenings on the photoresist. The resulting openings are formed on thetop of the electrical conductive pads of the circuit board, such thatthe conductive layer is used as a conductor so as to form the conductivebumps over the electrical conductive pads, or the double-layer structureconsisting of the base metal and the conductive bumps by electroplating.According, the present invention reduces the difficulty in alignment ofstencil printing in the prior art. Additionally, conductive bumps formedby electroplating has a stronger bonding than the prior art, and thatfiner pitch between the bumps can be achieved.

Moreover, conductive bumps can be quickly and precisely formed on thecircuit board using the processing apparatus of the present invention,thereby enhancing processing reliability.

Although the present invention has been described in accordance with theembodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations to the embodiments and thosevariations would be within the spirit and scope of the presentinvention. Accordingly, many modifications may be made by one ofordinary skill in the art without departing from the spirit and scope ofthe appended claims.

1. A processing apparatus for electroplating conductive bumps on anorganic circuit board, comprising: a surface cleaning unit for removingorganic contaminant from an exposed surface of a conductive layer of thecircuit board; a rinsing unit for rinsing the surface of the conductivelayer; a surface activating unit for removing a metal oxide formed onthe surface of the conductive layer; and an electroplating unit forelectroplating conductive bumps on the surface of the conductive layer.2. The processing apparatus of claim 1, wherein the circuit boardfurther comprises a plurality of electrical conductive pads for theconductive layer and the conductive bumps to be formed thereon.
 3. Theprocessing apparatus of claim 2, wherein the circuit board furthercomprises an insulating protective layer with patterned openings forexposing the electrical conductive pads, the conductive layer beingformed on the insulating protective layer and covering the electricalconductive pads, and a photoresist having openings corresponding to theelectrical conductive pads of the circuit board being formed on theconductive layer to partially expose the conductive layer overlying theelectrical conductive pads.
 4. The processing apparatus of claim 1,further comprising a post-treatment unit.
 5. The processing apparatus ofclaim 4, wherein the post-treatment unit comprises a rinsing unit and acleaning unit.
 6. The processing apparatus of claim 1, wherein thesurface cleaning unit comprises a cleanser to remove the organiccontaminant on the surface of the conductive layer of the circuit board.7. The processing apparatus of claim 6, wherein the cleanser comprises asurfactant.
 8. The processing apparatus of claim 1, wherein theconductive bumps are selected from the group consisting of copper, tin,lead, nickel, gold, silver, bismuth and their alloys.
 9. A processingapparatus for electroplating conductive bumps on an organic circuitboard, comprising: a surface cleaning unit for removing organiccontaminant from an exposed surface of a conductive layer of the circuitboard; a first rinsing unit for rinsing the surface of the conductivelayer; a first surface activating unit for removing a metal oxide formedon the surface of the conductive layer; a first electroplating unit forforming a base metal on the surface of the conductive layer; a secondrinsing unit for rinsing the surface of the base metal; and a secondelectroplating unit for electroplating conductive bumps on the surfaceof the base metal.
 10. The processing apparatus of claim 9, furthercomprising a second surface activating unit for removing a metal oxideformed on the surface of the base metal.
 11. The processing apparatus ofclaim 9, wherein the circuit board further comprises a plurality ofelectrical conductive pads for the conductive layer and the conductivebumps to be formed thereon.
 12. The processing apparatus of claim 11,wherein the circuit board further comprises an insulating protectivelayer with patterned openings for exposing the electrical conductivepads, the conductive layer being formed on the insulating protectivelayer and covering the electrical conductive pads, and a photoresisthaving openings corresponding to the electrical conductive pads of thecircuit board being formed on the conductive layer to partially exposethe conductive layer overlying the electrical conductive pads.
 13. Theprocessing apparatus of claim 9, further comprising a post-treatmentunit.
 14. The processing apparatus of claim 13, wherein thepost-treatment unit comprises a rinsing unit and a cleaning unit. 15.The processing apparatus of claim 9, wherein the first surface cleaningunit comprises a cleanser to remove the organic contaminant on thesurface of the conductive layer of the circuit board.
 16. The processingapparatus of claim 15, wherein the cleanser comprises a surfactant. 17.The processing apparatus of claim 9, wherein the conductive bumps areselected from the group consisting of copper, tin, lead, nickel, gold,silver, bismuth and their alloys.